U.S. Pat. Nos. 6,055,484 and 5,937,370 represent a recent, significant development in the field of tool monitoring and assembly qualifying. The programmed microprocessor is configured to identify a portion of the signal representative of the analog signal corresponding to a completed cycle. The configuration also allows for identification of an incomplete cycle and a multiple counting of a completed cycle (double-hit). A completed cycle occurs when a tool drives a fastener to completion causing the tool's mechanical clutch to end the cycle. An incomplete cycle occurs when a tool drives a fastener and the clutch is not allowed to complete the cycle by turning the tool off, meaning that the proper torque is never reached. A double-hit occurs when a tool drives a fastener that has previously been tightened to the target torque. The qualifiers and disclosures of U.S. Pat. Nos. 6,055,484 and 5,937,370 are herein incorporated by reference.
The next generation qualifier uses multiple thresholds and multiple timers to perform its operations. This version makes use of up to four thresholds and five timers in order to accomplish its qualification of an assembly process. This system for monitoring analog signatures is a function of the analog signal, and a programmed microprocessor configured to identify a portion of the analog signal corresponding to the parameter. The programmed microprocessor is configured to identify and store the parameter of a first threshold analog signal to begin monitoring and storing the parameter of a cycle. Next, the programmed microprocessor is configured to identify and store the parameter of a second analog level of the tool driving the fastener to its target torque and configured to identify and store the parameter of a third analog level to count a completed cycle when the measured analog signal is in the same as the third identified and stored parameter. Finally, the programmed microprocessor is configured to identify and store the parameter of a fourth analog level which indicates the shut off region of the cycle when the measured analog signal is above the fourth identified and stored parameter. See U.S. Pat. No. 6,567,754 which is herein incorporated by reference.